Hamner (whose brother Garvin was also an infielder in the majors) spent ​151⁄2 years with the Phillies, coming to the club as a 17-year-old during World War II and becoming one of the team leaders of the 1950 champions at the age of 23. A right-handed hitting shortstop with power, Hamner compiled more than 80 runs batted in four times. In the 1950 World Series, a four-game New York Yankees sweep dominated by Yankee pitchers, Hamner batted .429 (6 for 14) with three extra-base hits. In March 1952, Hamner was named captain of the Phillies by manager Eddie Sawyer.[1]

An All-Star three years in a row, Hamner was the National League's starting shortstop in the 1952 All-Star Game, played on his home field, Shibe Park, in Philadelphia. The game was called off after five innings due to rain.

On May 16, 1959, Hamner was traded to Cleveland, but he batted only .164 for the remainder of the campaign. He then became a manager in the minor league system of the Kansas City Athletics, reappearing briefly with the A's as a pitcher during the 1962 season (he had dabbled on the mound for the 1956-57 Phillies).[2] But the change did not prolong Hamner's playing career. He briefly managed in the Phils' farm system in the 1970s and 1980s.